The 62-year-old was told by doctors at Medway NHS Foundation Trust that he had a small tumour on his pancreas during an endoscopy procedure to investigate his symptoms.

He was then referred to King's College Hospital NHS Foundation Trust for surgery but medics there failed to act upon the diagnosis of possible cancer and investigated him for other problems.

His wife Jean - to whom he was married for 42 years and had three children with - ended up taking her complaint to the Parliamentary and Health Service Ombudsman (PHSO).

After investigating for a year, it ruled that King's failed to act quickly enough and had given the family "confusing and contradictory" information.

Mrs Filipovic, 65, from Sittingbourne, Kent, said: "The specialist at Medway said he had known people who had had this operation for a small tumour and had survived.

"He then referred Peter to King's for surgery, saying they were the best ones for this operation. But King's did absolutely nothing.

"We had to wait more than a month for our appointment at King's. They asked a few questions and then said we could go. They didn't mention an operation.

"We then waited another month for an appointment where Peter asked about the operation and the doctor said "what operation?"

"We said "for the cancer" and the doctor said "you haven't got cancer." We obviously felt relieved."

However, Mr Filipovic, who had two grandchildren, continued to lose enormous amounts of weight - he dropped from 18st to 12st in less six months - and suffered jaundice.

Mrs Filipovic said: "He looked terrible, he was completely yellow, even his eyeballs, and he was only eating small amounts.

"When we went back to King's, they decided to admit him. They did an endoscopy, saw the tumour and took a sample and then sent him home.

"About a month later we had another appointment and Peter couldn't even walk, he was in a wheelchair. They then said he did have cancer."

King's said it intended to operate but by then it was too late and Mr Filipovic was too weak to have the operation. The trust referred him for chemotherapy but it was also too late for that.

A damning report from the PHSO published on Tuesday - detailing dozens of errors by public bodies and the NHS - found King's failed to act quickly and mishandled the complaint.

While it was unable to ascertain whether the delays could have changed the outcome for Mr Filipovic, it ruled King's "failed to act on another trust's diagnosis of possible pancreatic cancer."

The report said: "Mr W (Filipovic) was diagnosed with suspected pancreatic cancer by Trust A (Medway) in late 2011 and was referred to Trust B (King's) for treatment.

"Trust B conducted its own tests, but did not treat Mr W for the suspected cancer. Mr W continued having tests in early 2012, and at the end of a two-month period Trust B confirmed that Mr W had pancreatic cancer.

"The Trust said that it intended to operate in approximately two weeks' time but unfortunately, by then, Mr W was too jaundiced to have the operation.

"The next month, when his jaundice had improved, Mr W was too frail to have the operation. The Trust referred him for chemotherapy but it was too late to treat him, and he died in summer 2012."

It said King's "ruled out possible pancreatic cancer" and instead "concentrated on changes in the body and another part of the pancreas.

"It failed to act quickly enough on Mr W's symptoms. However, the outcome might have been the same even if Trust B had been quicker with Mr W's investigations."

Parliamentary and Health Service Ombudsman Julie Mellor said: "The NHS provides excellent care for patients every day, which is why it is so important that when mistakes are made they are dealt with well.

"These cases bring home all the suffering patients and their families experience when things go wrong, particularly when complaints are not handled effectively at a local level.

"Families have been left without an explanation as to why their loved ones died, mistakes have not been admitted, which means that much-needed service improvements are being delayed."

Following the PHSO's investigation, King's apologised for the failings and the impact those failings had on Mrs Filipovic.

It also paid her £1,500 "in recognition that its failings denied Mr W the opportunity to be given the best chance of survival, and for the delay in providing a reasonable response to her complaint," the PHSO said.

A spokeswoman for King's College Hospital NHS Foundation Trust, said: "We would like to apologise wholeheartedly once again to the family involved in this case.

"The care Mr Filipovic received at the hospital fell below the high standards we set ourselves, and we recognise this was unacceptable.

"Lessons have been learnt from this case, and we have taken a number of steps to improve the safety of the services we provide."